Semiconductor device

ABSTRACT

One exemplary embodiment includes a semiconductor device. The semiconductor device comprising a channel including one or more of a metal oxide including zinc-gallium, cadmium-gallium, cadmium-indium.

Semiconductor devices are used in a variety of electronic devices. Forexample, thin-film transistor technology can be used in liquid crystaldisplay (LCD) screens. Some types of thin-film transistors haverelatively slow switching speeds because of low carrier mobility. Insome applications, such as LCD screens, use of thin-film transistorswith relatively slow switching speeds can make it difficult toaccurately render motion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1F illustrate various embodiments of a semiconductor device,such as a thin-film transistor.

FIG. 2 illustrates a cross-sectional schematic of an embodiment of athin-film transistor.

FIG. 3 illustrates a method embodiment for manufacturing an embodimentof a thin-film transistor.

FIG. 4 illustrates an embodiment of an active matrix display area.

DETAILED DESCRIPTION

The exemplary embodiments of the present disclosure includesemiconductor devices, such as transistors, that contain multicomponentoxide semiconductors. Additionally, exemplary embodiments of the presentdisclosure account for the properties possessed by transistors thatcontain multicomponent oxide semiconductors, e.g. optical transparency,and electrical performance. Exemplary embodiments include semiconductordevices having multicomponent oxide semiconductor structures thatinclude at least one metal cation from group 12 and at least one metalcation from group 13 to form at least one of a three-component oxide, afour-component oxide, and a two-component oxide that includeszinc-gallium oxide, cadmium-gallium oxide, and cadmium-indium oxide. Insome of the exemplary embodiments, the multicomponent oxidesemiconductor structure can include an amorphous form, a single-phasecrystalline state, or a mixed-phase crystalline state. As used herein,the terms multicomponent oxide, multicomponent oxide, and multicomponentoxide material, are intended to mean oxide material systems that caninclude two, three, and four-component oxide materials formed from metalcations of group 12 (group IIB of the CAS) and group 13 (group IIIA ofthe CAS) of the periodic table of the elements.

Unless otherwise indicated, all numbers expressing quantities ofingredients, reaction conditions, and so forth used in the specificationand claims are to be understood as being modified in all instances bythe term “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that may vary depending upon thedesired properties sought to be obtained by the present disclosure. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claims, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

It should be understood that the various semiconductor devices may beemployed in connection with the various embodiments of the presentdisclosure, i.e., field effect transistors including thin-filmtransistors, active matrix displays, logic inverters, and amplifiers.FIGS. 1A-1F illustrate various embodiments of a semiconductor device,such as a thin-film transistor. The thin-film transistor can be of anytype, including but not limited to, horizontal, vertical, coplanarelectrode, staggered electrode, top-gate, bottom-gate, single-gate, anddouble-gate, to name a few.

As used herein, a coplanar electrode configuration is intended to mean atransistor structure where the source and drain electrodes arepositioned on the same side of the channel as the gate electrode. Astaggered electrode configuration is intended to mean a transistorstructure where the source and drain electrodes are positioned on theopposite side of the channel as the gate electrode.

FIGS. 1A and 1B illustrate embodiments of bottom-gate transistors, FIGS.1C and 1D illustrate embodiments of top-gate transistors, and FIGS. 1Eand 1F illustrate embodiments of double-gate transistors. In each ofFIGS. 1A-1D, the transistors include a substrate 102, a gate electrode104, a gate dielectric 106, a channel 108, a source electrode 110, and adrain electrode 112. In each of FIGS. 1A-1D, the gate dielectric 106 ispositioned between the gate electrode 104 and the source and drainelectrodes 110, 112 such that the gate dielectric 106 physicallyseparates the gate electrode 104 from the source and the drainelectrodes 110, 112. Additionally, in each of the FIGS. 1A-1D, thesource and the drain electrodes 110, 112 are separately positionedthereby forming a region between the source and drain electrodes 110,112 for interposing the channel 108. Thus, in each of FIGS. 1A-1D, thegate dielectric 106 is positioned adjacent the channel 108, andphysically separates the source and drain electrodes 110, 112 from thegate electrode 104. Additionally, in each of the FIGS. 1A-1D, thechannel 108 is positioned adjacent the gate dielectric 106 and isinterposed between the source and drain electrodes 110, 112.

In various embodiments, such as in the double-gate embodiments shown inFIGS. 1E and 1F, two gate electrodes 104-1, 104-2 and two gatedielectrics 106-1, 106-2 are illustrated. In such embodiments, thepositioning of the gate dielectrics 106-1, 106-2 relative to the channel108 and the source and drain electrodes 110, 112, and the positioning ofthe gate electrodes 104-1, 104-2 relative to the gate dielectrics 106-1,106-2 follow the same positioning convention described above where onegate dielectric and one gate electrode are illustrated. That is, thegate dielectrics 106-1, 106-2 are positioned between the gate electrodes104-1, 104-2 and the source and drain electrodes 110, 112 such that thegate dielectrics 106-1, 106-2 physically separate the gate electrodes104-1, 104-2 from the source and the drain electrodes 110, 112.

In each of FIGS. 1A-1F, the channel 108 interposed between the sourceand the drain electrodes 110, 112 provide a controllable electricpathway between the source and drain electrodes 110, 112 such that whena voltage is applied to the gate electrode 104, an electrical charge canmove between the source and drain electrodes 110, 112 via the channel108. The voltage applied at the gate electrode 104 can vary the abilityof the channel 108 to conduct the electrical charge and thus, theelectrical properties of the channel 108 can be controlled, at least inpart, through the application of a voltage at the gate electrode 104.

A more detailed description of an embodiment of a semiconductor devicesuch as a thin-film transistor is illustrated in FIG. 2. FIG. 2illustrates a cross-sectional view of an exemplary bottom gate thin-filmtransistor 200. It will be appreciated that the different layers of thethin-film transistor described in FIG. 2, the materials in which theyconstitute, and the methods in which they are formed can be equallyapplicable to any of the transistor embodiments described herein,including those described in connection with FIGS. 1A-1F. Moreover, inthe various embodiments, the thin-film transistor 200 can be included ina number of devices including an active matrix display screen device, alogic inverter, and an amplifier. The thin-film transistor 200 can alsobe included in an infrared device, where transparent components are alsoused.

As shown in FIG. 2, the thin-film transistor 200 can include a substrate202, a gate electrode 204 positioned adjacent the substrate 202, a gatedielectric 206 positioned adjacent the gate electrode 204, and a channel208 positioned between the gate dielectric 206, a source electrode 210,and a drain electrode 212. In the embodiment shown in FIG. 2, thesubstrate 202 includes glass. However, substrate 202 can include anysuitable substrate material or composition for implementing the variousembodiments.

The substrate 202 illustrated in FIG. 2 includes a blanket coating ofITO, i.e., indium-tin oxide to form the gate electrode 204 layer.However, any number of materials can be used for the gate electrode 204.Such materials can include transparent materials such as an n-type dopedIn₂O₃, SnO₂, or ZnO, and the like. Other suitable materials includemetals such as In, Sn, Ga, Zn, Al, Ti, Ag, Cu, and the like. In theembodiment illustrated in FIG. 2, the thickness of the gate electrode204 is approximately 200 nm. The thickness of a gate electrode layer canvary depending on the materials used, device type, and other factors.

The gate dielectric 206 shown in FIG. 2 is also blanket coated. Althoughthe gate electrode 204 and gate dielectric 206 are shown as blanketcoated, unpatterned layers in FIG. 2, they can be patterned. In thevarious embodiments, the gate dielectric layer 206 can include variouslayers of different materials having insulating propertiesrepresentative of gate dielectrics. Such materials can include tantalumpentoxide (Ta₂O₅), Strontium Titanate (ST), Barium Strontium Titanate(BST), Lead Zirconium Titanate (PZT), Strontium Bismuth Tantalate (SBT)and Bismuth Zirconium Titanate (BZT), silicon dioxide (SiO₂), siliconnitride (Si₃N₄), magnesium oxide (MgO), aluminum oxide (Al₂O₃),hafnium(IV)oxide (HfO₂), zirconium(IV)oxide (ZrO₂), various organicdielectric material, and the like.

In various embodiments, the gate dielectric 206 may be deposited by alow-pressure CVD process using Ta(OC₂H₅)₅ and O₂ at about 430° C., andmay be subsequently annealed in order to reduce leakage currentcharacteristics. Other methods for introducing the gate dielectric layercan include various CVD and sputtering techniques and atomic layerdeposition, evaporation, and the like as will be described in moredetail herein.

In the various embodiments, the source electrode 210 and the drainelectrode 212 are separately positioned adjacent the gate dielectric206. In the embodiment shown in FIG. 2, the source and drain electrodes210, 212 can be formed from the same materials as those discussed inregards to the gate electrode 204. In FIG. 2, the source and drainelectrodes 210, 212 have a thickness of approximately 200 nm. However,the thickness can vary depending on composition of material used,application in which the material will be used, and other factors. Thechoice of source and drain electrode material can vary depending on theapplication, device, system, etc., in which they will be used. Overalldevice performance is likely to vary depending on the source and drainmaterials. For example, in devices where a substantially transparentthin-film transistor is desired, the materials for the source, drain,and gate electrodes can be chosen for that effect.

In the various embodiments, the channel 208 can be formed from amulticomponent oxide material that includes two, three, andfour-component oxides that include metal cations from group 12 and group13 of the periodic table of elements. As used herein, a multicomponentoxide is intended to mean a two, three, and four-component oxide thatcan include various metal cations of groups 12 and 13, as disclosedherein. Additionally, in the various embodiments including two, three,and four component oxides, each component is different. Thus, atwo-component oxide can include two different metal cations, and afour-component oxide can include four different metal cations.

In the various embodiments, the channel can be described as includingone or more compounds of a formula, as described herein. In the variousembodiments, the formula can be characterized by a series of lettersthat include A, B, C, D (representing cations as described herein), andO (atomic oxygen). The formula can also be characterized by a subscriptx of the series of letters, e.g. Ax. In the formula, the letters, otherthan O, are intended to denote the identity of a metal cation selectedfrom a defined group, and the subscripts are intended to denote theidentity of the metal cation selected from the defined group. Forexample, if A represents the metal cation Zn, and x represents thenumber 2, then A_(x) can include Zn₂, e.g., two atoms of Zn.

Additionally, the letter O denotes atomic oxygen as characterized by thesymbol O on the periodic table of the elements. Thus, depending on thestoichiometry of a compound derived from a formula, the subscript of O,i.e., O_(x), in the formula can vary depending on the number of atoms ofmetal cations included in any given formula. For example, the formulaA_(x)B_(x)O_(x) can include the binary metal oxide: zinc-gallium oxidehaving the stoichiometric arrangement: Zn₂Ga₂O₅, wherein O₅ denotes thenumber of oxygen atoms associated with this combination of ZnO andGa₂O₃.

In the formulas described herein, at least one metal cation from each ofgroups 12 and 13 are included in the multicomponent oxide material. Forexample, the formula A_(x)B_(x)C_(x)O_(x) can include a variety ofthree-component oxides formed from the selection of at least one group12 and at least one group 13 metal cation. Thus, in a multicomponentoxide having two, three, or four components, at least one metal cationfrom each of groups 12 and 13 are included. Additionally, a selectedmetal cation in any given formula is selected one time. That is, in theformula, A_(x)B_(x)C_(x)O_(x), if A is selected to be zinc, then neitherB nor C can include zinc.

In various embodiments, the channel 208 can be formed from amulticomponent oxide material that includes one of a ternary metal oxideincluding: zinc-gallium oxide, cadmium-gallium oxide, and cadmium-indiumoxide. In these embodiments, the metal oxide can include an atomiccomposition of metal(A)-to-metal(B) ratio (A:B), where A and B canindependently take values from about 0.05 to about 0.95. Thus, azinc-gallium oxide can include an atomic composition having a relativeconcentration of 0.05 zinc and 0.95 gallium or 0.95 zinc and 0.05gallium. That is, the channel according to this embodiment can includevarious two-component oxides having an atomic composition of eachcomponent falling within the range of about 0.05 to about 0.95.

In various embodiments, the channel 208 can be formed from amulticomponent oxide material that includes one or more compounds of theformula A_(x)B_(x)C_(x)O_(x). In such embodiments, each A can beselected from the group of Zn, Cd, each B can be selected from the groupof Ga, In, each C can be selected from the group of Zn, Cd, Ga, In, eachO can be atomic oxygen, each x can be independently a non-zero integer,and each of A, B, and C are different. That is, the value of “x” foreach of the constituent elements may be different and in the embodimentof formula A_(x)B_(x)C_(x)O_(x), if B is zinc, then A or C will notinclude zinc. In these embodiments, according to the formulaA_(x)B_(x)C_(x)O_(x), four three-component oxides can be formed. Thefour three-component oxides can include: zinc-gallium-indium oxide,cadmium-gallium-indium oxide, zinc-cadmium-gallium oxide, andzinc-cadmium-indium oxide. Further, in these embodiments, the one ormore compounds of the formula A_(x)B_(x)C_(x)O_(x) can include an atomiccomposition of ratio A:B:C, wherein A, B, and C, are each in a range ofabout 0.025 to about 0.95. Thus, for example, a zinc-gallium-indiumoxide can include a concentration having a ratio, near ends of a range,of about 0.025 zinc, 0.025 gallium, and 0.95 indium or about 0.95 zinc,0.025 gallium, and 0.025 indium or about 0.025 zinc, 0.95 gallium, and0.025 indium or ratios of zinc/gallium/indium in between the ratio nearends of the range. That is, the channel according to this embodiment caninclude various three-component oxides having atomic composition ratioswith the relative concentration of each component falling within therange of about 0.025 to about 0.95.

In one embodiment, the channel 208 can be formed from a multicomponentoxide material that includes one or more compounds of the formulaA_(x)B_(x)C_(x)D_(x)O_(x). In this embodiment, each A can be selectedfrom the group of Zn, Cd, each B can be selected from the group of Ga,In, each C can be selected from the group of Zn, Cd, Ga, In, each D canbe selected from the group of Zn, Cd, Ga, In, each O can be atomicoxygen, and each x can be independently a non-zero integer. That is, thevalue of “x” for each of the constituent elements may be different.Thus, in this embodiment, a four-component oxide can be formed thatincludes a zinc-cadmium-gallium-indium oxide. In this embodiment, theone or more compounds of the formula A_(x)B_(x)C_(x)D_(x)O_(x) caninclude an atomic composition of ratio A:B:C:D wherein A, B, C, and D,are each in a range of about 0.017 to about 0.95. Thus, thezinc-cadmium-gallium-indium oxide can include an atomic compositionhaving a ratio, near ends of a range, of about 0.017 zinc, 0.017cadmium, 0.017 gallium, and 0.95 indium or ratios ofzinc/cadmium/gallium/indium in between the ratio near ends of the range.That is, the channel according to this embodiment can include afour-component oxide having atomic composition ratios with the relativeconcentration of each component falling within the range of about 0.017to about 0.95.

As one of ordinary skill will understand, the atomic composition ratiosof metal cations for any given two, three, and four component oxides arenot limited to the ratios in the foregoing embodiments. In variousembodiments, each of the two, three, and four component oxides can beformed having a variety of atomic composition ratios. For example, athree-component oxide can include an atomic composition having a ratioof 0.025 zinc, 0.485 gallium, and 0.49 indium.

In the various embodiments, the multicomponent oxide can include variousmorphologies depending on composition, processing conditions, and otherfactors. The various morphological states can include amorphous states,and polycrystalline states. A polycrystalline state can include asingle-phase crystalline state or a mixed-phase crystalline state.Additionally, in the various embodiments, the source, drain, and gateelectrodes can include a substantially transparent material. By usingsubstantially transparent materials for the source, drain, and gateelectrodes, areas of the thin-film transistor can be transparent to theportion of the electromagnetic spectrum that is visible to the humaneye. In the transistor arts, a person of ordinary skill will appreciatethat devices such as active matrix liquid crystal displays havingdisplay elements (pixels) coupled to thin-film transistors (TFT's)having substantially transparent materials for selecting or addressingthe pixel to be on or off will improve display performance by allowingmore light to be transmitted through the display.

Referring back to FIG. 2, the channel 208 can be formed from amulticomponent oxide with a channel thickness of about 50 nm, however,in various embodiments the thickness of the channel can vary dependingon a variety of factors including whether the channel material isamorphous or polycrystalline, and the device in which the channel is tobe incorporated.

In this embodiment, the channel 208 is positioned adjacent the gatedielectric 206 and between the source and drain electrodes 210, 212. Anapplied voltage at the gate electrode 204 can facilitate electronaccumulation or depletion in the channel 208. In addition, the appliedvoltage can enhance electron injection from the source electrode 210 tothe channel 208 and electron extraction therefrom by the drain electrode212. In the embodiments of the present disclosure, the channel 208 canallow for on/off operation by controlling current flowing between thedrain electrode 212 and the source electrode 210 using a voltage appliedto the gate electrode 204.

In various embodiments, the channel 208 can include a multicomponentoxide material with at least one metal cation selected from group 12,and at least one metal cation selected from group 13, wherein group 12metal cations can include Zn and Cd, and group 13 metal cations caninclude Ga and In, to form at least one of a three-component oxide, afour-component oxide, and a two-component oxide that includeszinc-gallium oxide, cadmium-gallium oxide, cadmium-indium oxide.Additionally, in the various embodiments, each component in themulticomponent oxide material is different. For example, where amulticomponent oxide includes three metal cations, i.e., athree-component oxide, the same two cations will not be included in thethree-component oxide, thus, if zinc is included in the three-componentoxide, it will not be included as a second or third component of thethree-component oxide. In another example, if zinc is a component of afour-component oxide, the other three components of the four-componentoxide will not include zinc. These atomic compositions do not take intoconsideration the optional presence of oxygen and other elements. Theyare merely a representation of the selection of cations for themulticomponent oxide material used for the channel of a thin-filmtransistor.

The multicomponent oxides, as described herein, can provide verysatisfactory electrical performance, specifically in the area of channelmobility. As appreciated by one skilled in the art, mobility is acharacteristic that can help in determining thin-film transistorperformance, as maximum operating frequency, speed, and drive currentincrease in direct proportion to channel mobility. In addition, thechannel can be transparent in both the visible and near-infraredspectrums, allowing for an entire thin-film transistor to be opticallytransparent throughout the visible region of the electromagneticspectrum.

The use of the multicomponent oxide channel illustrated in theembodiments of the present disclosure is beneficial for a wide varietyof thin-film applications in integrated circuit structures. For example,such applications include transistors, as discussed herein, such asthin-film transistors, horizontal, vertical, coplanar electrode,staggered electrode, top-gate, bottom-gate, single-gate, anddouble-gate, to name only a few. In the various embodiments, transistors(e.g., thin-film transistors) of the present disclosure can be providedas switches or amplifiers, where applied voltages to the gate electrodesof the transistors can affect a flow of electrons through the channel.As one of ordinary skill will appreciate, transistors can operate in avariety of ways. For example, when a transistor is used as a switch, thetransistor can operate in the saturation region, and where a transistoris used as an amplifier, the transistor can operate in the linearregion. In addition, the use of transistors incorporating channels of amulticomponent oxide in integrated circuits and structures incorporatingintegrated circuits such as visual display panels (e.g., active matrixLCD displays) such as that shown and described in connection with FIG. 4below. In display applications and other applications, it will often bedesirable to fabricate one or more of the remaining thin-film transistorlayers, e.g., source, drain, and gate electrodes, to be at leastpartially transparent.

In FIG. 2, the source electrode 210 and the drain electrode 212 includean ITO layer having a thickness of about 200 nm. In the variousembodiments however, the thickness can vary depending on a variety offactors including type of materials, applications, and other factors. Invarious embodiments, the source and drain electrodes 210, 212, mayinclude a transparent conductor, such as an n-type doped wide-bandgapsemiconductor. Examples include, but are not limited to, n-type dopedIn₂O₃, SnO₂, indium-tin oxide (ITO), or ZnO, and the like. The sourceand drain electrodes 210, 212 may also include a metal such as In, Sn,Ga, Zn, Al, Ti, Ag, Cu, Au, Pt, W, or Ni, and the like. In the variousembodiments of the present disclosure, all of the electrodes 204, 210,and 212 may include transparent materials such that the variousembodiments of the transistors may be made substantially transparent.

The various layers of the transistor structures described herein can beformed using a variety of techniques. For example, the gate dielectric206 may be deposited by a low-pressure CVD process using Ta(OC₂H₅)₅ andO₂ at about 430° C., and may be subsequently annealed in order to reduceleakage current characteristics. Thin-film deposition techniques such asevaporation (e.g., thermal, e-beam), physical vapor deposition (PVD)(e.g., dc reactive sputtering, rf magnetron sputtering, and ion beamsputtering), chemical vapor deposition (CVD), atomic layer deposition(ALD), pulsed laser deposition (PLD), molecular beam epitaxy (MBE), andthe like may be employed. Additionally, alternate methods may also beemployed for depositing the various transistor layers of the embodimentsof the present disclosure. Such alternate methods can includeanodization (electrochemical oxidation) of a metal film, as well asdeposition from a liquid precursor such as spin coating and ink-jetprinting including thermal and piezoelectric drop-on-demand printing.Film patterning may employ photolithography combined with etching orlift-off processes, or may use alternate techniques such as shadowmasking. Doping of one or more of the layers (e.g., the channelillustrated in FIG. 2) may also be accomplished by the introduction ofoxygen vacancies and/or substitution of aliovalent elements.

Embodiments of the present disclosure also include methods of formingmetal containing films on a surface of a substrate or substrateassembly, such as a silicon wafer, with or without layers or structuresformed thereon, used in forming integrated circuits, and in particularthin-film transistors as described herein. It is to be understood thatmethods of the present disclosure are not limited to deposition onsilicon wafers; rather, other types of wafers (e.g., gallium arsenide,glass, etc.) can be used as well.

Furthermore, other substrates can also be used in methods of the presentdisclosure. These include, for example, fibers, wires, etc. In general,the films can be formed directly on the lowest surface of the substrate,or they can be formed on any of a variety of the layers (i.e., surfaces)as in a patterned wafer, for example.

In FIG. 3, a method for fabricating a semiconductor device isillustrated. In the various embodiments of the present disclosure, asubstrate or substrate assembly can be provided in forming thesemiconductor structure. As used herein, the term “substrate” refers tothe base substrate material layer, e.g., the lowest layer of glassmaterial in a glass wafer. The term “substrate assembly” refers to thesubstrate having one or more layers or structures formed thereon.Examples of substrate types include, but are not limited to, glass,plastic, and metal, and include such physical forms as sheets, films,and coatings, among others, and may be opaque or substantiallytransparent.

In block 310, a drain electrode and a source electrode can both beprovided. For example, both the drain electrode and the source electrodecan be provided on the substrate of substrate assembly.

In the various embodiments, precursor compounds are described as metals,oxides of metals, multicomponent oxides, and formulas having letters andsubscripts. In formulas, the letters, e.g., A, are intended to denote ametal cation selected from a defined group and the subscripts, e.g., x,are intended to denote the number of atoms of the metal cation selectedfrom the defined group. Additionally, a compound as used herein caninclude two or more elements including metal cations from groups 12 and13, and oxygen. The precursor compounds described herein do not indicatethe presence of O_(x); however, as one of ordinary skill will understandthe precursor compounds can also include oxygen to provide the oxide ofthe compound. In other words, many of the precursor compounds listedbelow are provided as multicomponent metals, i.e., metal-metalcompounds. The below described method is not intended to limit thecompounds by excluding oxygen. As one of ordinary skill will understand,oxygen can be included in the precursor compounds in the variousdeposition techniques described herein.

Various combinations of the precursor compounds described herein can beused in a precursor composition. Thus, as used herein, a “precursorcomposition” refers to a solid or liquid that includes one or moreprecursor compounds described herein optionally mixed with one or moreprecursor compounds other than those described herein. For example, zincprecursor compounds and gallium precursor compounds can be provided inone precursor composition or in separate compositions. Where they areincluded in separate compositions, both precursor compositions areincluded when a channel is deposited.

In block 320, a channel contacting the drain electrode and the sourceelectrode, and including a multicomponent oxide, can be deposited. Forexample, the channel can be deposited between the drain electrode and asource electrode so as to electrically couple the two electrodes. In thevarious embodiments, depositing the channel contacting the drainelectrode and the source electrode can include providing at least oneprecursor composition including one or more precursor compounds thatinclude: zinc-gallium oxide, cadmium-gallium oxide, and cadmium-indiumoxide can be provided. For example, zinc precursor compounds and cadmiumprecursor compounds can be provided in one precursor composition or inseparate compositions. Thus, a precursor composition according to theseembodiments can include binary metal oxides, i.e., zinc oxide, and othermulticomponent metal oxides, i.e., zinc-gallium oxide. Where a precursorcomposition includes a binary metal oxide, an additional precursorcomposition including a different binary metal oxide can be includedwhen depositing a channel, thereby forming a channel that includes amulticomponent metal oxide, such as a zinc-gallium oxide.

Additionally, in various embodiments, the precursor composition canfurther include one or more precursor compounds that include A_(x), oneor more precursor compounds that include B_(x), and one or moreprecursor compounds that include C_(x).

In such embodiments, each A can be selected from the group of Zn, Cd,each B can be selected from the group of Ga, In, each C can be selectedfrom the group of Zn, Cd, Ga, In, each x can be independently a non-zerointeger, and each of A, B, and C are different. That is, the value of“x” for each of the constituent elements may be different. Thus, inthese embodiments, at least one metal cation from a group defined by A,at least one metal cation from a group defined by B, and at least onemetal cation from a group defined by C can be provided to form one ormore precursor compositions of one or more compounds of A_(x), B_(x),and C_(x). For example, a precursor composition according to theseembodiments can include precursor compounds of Ax, Bx, and Cx.Additionally, a precursor compound according to these embodiments caninclude compounds of Ax and Cx. In such a case, an additional precursorcomposition including Bx can be included when depositing a channel,thereby forming a channel that includes a quaternary metal oxide, i.e.,a three-component oxide.

In one embodiment, the precursor composition can further include one ormore precursor compounds that include D_(x). In this embodiment, each A,B, and C can include those materials as described herein, and each D canbe selected from the group of Zn, Cd, Ga, In, each x can beindependently a non-zero integer, and each of A, B, C, and D aredifferent. That is, the value of “x” for each of the constituentelements may be different. Thus, in this embodiment, the precursorcomposition can include one or more compounds that include A_(x), B_(x),C_(x), and D_(x). In such an embodiment, at least one metal cation fromgroups defined by A, B, C, and D can be provided to form one or moreprecursor compositions of one or more compounds of A_(x), B_(x), C_(x),and D_(x). In this embodiment however, a deposited channel includes theprecursor compounds of A_(x), B_(x), C_(x), and D_(x), thereby forming achannel that includes a four-component oxide.

As used herein, “liquid” refers to a solution or a neat liquid (a liquidat room temperature or a solid at room temperature that melts at anelevated temperature). As used herein, a “solution” does not call forcomplete solubility of the solid; rather, the solution may have someundissolved material, more desireably, however, there is a sufficientamount of the material that can be carried by the organic solvent intothe vapor phase for chemical vapor deposition processing. The precursorcompounds as used herein can also include one or more organic solventssuitable for use in a chemical vapor deposition system, as well as otheradditives, such as free ligands, that assist in the vaporization of thedesired precursor compounds.

A wide variety of Zn, Cd, Ga, and In precursor compounds suitable forthin-film deposition techniques can be used with the embodiments of thepresent disclosure. Examples of the precursor compounds include, but arenot limited to, the metals and oxides of the metals, including ZnO,ZnO₂, CdO, GaO, Ga₂O, Ga₂O₃, InO, and In₂O₃ precursor compounds.Although specific precursor compounds are illustrated herein, a widevariety of precursor compounds can be used as long as they can be usedin a deposition process. In the various embodiments of the presentdisclosure, the Zn, Cd, Ga, and In precursor compounds can includeneutral precursor compounds and may be liquids or solids at roomtemperature. If they are solids, they are sufficiently soluble in anorganic solvent to allow for vaporization, they can be vaporized orsublimed, or ablated (e.g., by laser ablation or sputtering) from thesolid state, or they have melting temperatures below their decompositiontemperatures. Thus, many of the precursor compounds described herein aresuitable for use in vapor deposition techniques, such as chemical vapordeposition (CVD) techniques, (e.g., flash vaporization techniques,bubbler techniques, and/or microdroplet techniques).

The precursor compounds described herein can be used in precursorcompositions for ink-jet deposition, sputtering, and vapor depositiontechniques (e.g., chemical vapor deposition (CVD) or atomic layerdeposition (ALD)). Alternatively, certain precursor compounds describedherein can be used in precursor compositions for other depositiontechniques, such as spin-on coating, and the like. Typically, thoseprecursor compounds containing organic R groups with a low number ofcarbon atoms (e.g., 1-4 carbon atoms per R group) are suitable for usewith vapor deposition techniques. Those precursor compounds containingorganic R groups with a higher number of carbon atoms (e.g., 5-12 carbonatoms per R group) are generally suitable for spin-on or dip coating.

As used herein, the term “organic R groups” means a hydrocarbon group(with optional elements other than carbon and hydrogen, such as oxygen,nitrogen, sulfur, and silicon) that is classified as an aliphatic group,cyclic group, or combination of aliphatic and cyclic groups (e.g.,alkaryl and aralkyl groups). In the context of the present disclosure,the organic groups are those that do not interfere with the formation ofa metal-containing film. They may be of a type and size that do notinterfere with the formation of a metal-containing film using chemicalvapor deposition techniques. The term “aliphatic group” means asaturated or unsaturated linear or branched hydrocarbon group. This termis used to encompass alkyl, alkenyl, and alkynyl groups, for example.The term “alkyl group” means a saturated linear or branched hydrocarbongroup including, for example, methyl, ethyl, isopropyl, t-butyl, heptyl,dodecyl, octadecyl, amyl, 2-ethylhexyl, and the like. The term “alkenylgroup” means an unsaturated, linear or branched hydrocarbon group withone or more carbon-carbon double bonds, such as a vinyl group. The term“alkynyl group” means an unsaturated, linear or branched hydrocarbongroup with one or more carbon-carbon triple bonds. The term “cyclicgroup” means a closed ring hydrocarbon group that is classified as analicyclic group, aromatic group, or heterocyclic group. The term“alicyclic group” means a cyclic hydrocarbon group having propertiesresembling those of aliphatic groups. The term “aromatic group” or “arylgroup” means a mono- or polynuclear aromatic hydrocarbon group. The term“heterocyclic group” means a closed ring hydrocarbon in which one ormore of the atoms in the ring is an element other than carbon (e.g.,nitrogen, oxygen, sulfur, etc.).

Still referring to FIG. 3, the channel can be deposited including theprecursor composition to form a multicomponent oxide from the precursorcomposition to electrically couple a drain electrode and a sourceelectrode. In various embodiments, the channel can employ variousphysical vapor deposition techniques, such as dc reactive sputtering, rfsputtering, magnetron sputtering, and ion beam sputtering. Other methodsfor depositing the channel can include using an ink-jet depositiontechnique when the precursor composition includes a liquid form.

In the various embodiments, the multicomponent oxide included in thechannel can have a uniform composition throughout its thickness,although this is not a requisite. For example, in a four-componentoxide, a precursor composition including a precursor compound thatincludes A_(x) can be deposited first and then a combination ofprecursor compounds that include B_(x), C_(x), and D_(x) can bedeposited to form a four-component oxide channel. As will beappreciated, the thickness of the multicomponent oxide channel will bedependent upon the application for which it is used. For example, thethickness can have a range of about 1 nanometer to about 1,000nanometers. In an alternative embodiment, the thickness can have a rangeof about 10 nanometers to about 200 nanometers.

In the embodiments of the present disclosure, the multicomponent oxidecan include compounds of at least one metal cation from group 12, and atleast one metal cation from group 13, wherein the group 12 cationincludes Zn and Cd cations, and the group 13 cation includes Ga and Incations to form at least one of a three-component oxide, afour-component oxide, and a two-component oxide that includeszinc-gallium oxide, cadmium-gallium oxide, cadmium-indium oxide. Theprecursor compounds for group 12 and group 13 metal cations aretypically mononuclear (i.e., monomers in that they contain one metal permolecule), although weakly bound dimers (i.e., dimers containing twomonomers weakly bonded together through hydrogen or dative bonds) arealso possible. In additional embodiments of the present disclosure, theprecursor compounds used for forming the multicomponent oxide caninclude organometallic compounds suitable for vapor deposition. Exampleof such organometallic compounds include, but are not limited to, zincacethylacetonate [Zn(C₅H₇O₂)₂] and indium acethylacetonate[In(C₅H₇O₂)₃].

As discussed herein, the precursor compounds used for forming themulticomponent oxide in a sputtering process in the embodiments of thepresent disclosure can include two, three, and four-component oxides.For example, a two-component oxide can be used as a target to form thechannel. The two-component oxide can be deposited in a thin-film bysputtering by use of the above-mentioned target and a single-phasecrystalline state for the channel can be obtained. For illustration, asingle-phase crystalline state can include compounds from group 12, andcompounds from group 13, wherein group 12 includes an oxide of the metalcation Zn, such as ZnO, and group 13 includes an oxide of the metalcation Ga, such as Ga₂O₃, of the formula:Zn₂Ga_(2y)O_(x+3y)In this embodiment, the values of x and y can be found in given ranges.For example, x and y can each independently be found in a range of about1 to about 15, a range of about 2 to about 10, integer values greaterthan 1, and integer values less than 15. Specific examples of the valueof x and y include 2 and 1, respectively, where the single-phasecrystalline state of the zinc-gallium oxide includes Zn₂Ga₂O₅.

Alternatively, embodiments of the zinc-gallium oxide can exhibit amixed-phase crystalline state resulting from sputtering by use of theabove-mentioned target. For example, the mixed-phase crystalline statecan include, but is not limited to, two or more phases that can include,for example, ZnO, Zn₂Ga₂O₅, and Ga₂O₃ with a range of phase-to-phaseratio A:B:C (e.g., ZnO:Zn₂Ga₂O₅: Ga₂O₃), where A, B, and C, are each inthe range of about 0.01 to about 0.99.

Additionally, the compounds of the group 12 and group 13 cations canexhibit excellent electron transport in the amorphous state. As such, adesireable level of performance can be achieved without crystallizationof the multicomponent oxide. Thus, in various embodiments, thezinc-gallium oxide can have a substantially amorphous form. For example,the zinc-gallium oxide can include an atomic composition ofzinc(x):gallium (1-x), where x is in the range of about 0.01 to about0.99. This atomic composition does not take into consideration theoptional presence of oxygen and other elements. It is merely arepresentation of the relative ratio of zinc and gallium. In anadditional embodiment, x can be in the range of about 0.1 to about 0.9,and in the range of about 0.05 to about 0.95.

As one of ordinary skill will appreciate, in embodiments where three andfour-component oxides are used for channel formation by sputtering andother deposition techniques, the atomic compositions for each precursorcompound can include a range of about 0.01 to about 0.99. Additionally,other ranges can include a range of about 0.1 to about 0.9, and a rangeof about 0.05 to about 0.095.

Additionally, since each of these multicomponent oxide materials isbased on combination of groups 12 and 13 cations, a substantial degreeof qualitative similarity is expected in structural and electricalproperties, and in processing considerations. Furthermore, zinc-indiumoxide, a constituent of the two-component oxides disclosed herein hasbeen shown to exhibit excellent electron transport and thus,qualitatively similar performance from the remaining two-component oxidecombinations including the three, and four-component oxides can beexpected. An example of the electron transport characteristics of thezinc-indium oxide can be found in copending U.S. patent application Ser.No. 10/799,961 entitled “SEMICONDUCTOR DEVICE” filed on Mar. 12, 2004.

Sputtering or chemical vapor deposition processes can be carried out inan atmosphere of inert gas and/or a reaction gas to form a relativelypure multicomponent oxide channel. The inert gas is typically selectedfrom the group including nitrogen, helium, argon, and mixtures thereof.In the context of the present disclosure, the inert gas is one that isgenerally unreactive with the precursor compounds described herein anddoes not interfere with the formation of a multicomponent oxide channel.

The reaction gas can be selected from a wide variety of gases reactivewith the precursor compounds described herein, at least at a surfaceunder the conditions of deposition. Examples of reaction gases includehydrogen and oxidizing gases such as O₂. Various combinations of carriergases and/or reaction gases can be used in the embodiments of thepresent disclosure to form the multicomponent oxide channel.

For example, in a sputtering process for the multicomponent oxidechannel, the process may be performed by using a mixture of argon andoxygen as the sputtering gas at a particular flow rate, with theapplication of an RF power for achieving the desired deposition in asputter deposition chamber. However, it should be readily apparent thatany manner of forming the multicomponent oxide channel is contemplatedin accordance with the present disclosure and is in no manner limited toany particular process, e.g., sputtering, for formation thereof.

In block 330, both a gate electrode and a gate dielectric positionedbetween the gate electrode and the channel can be provided in forming anembodiment of the thin-film transistor of the present disclosure.

The embodiments described herein may be used for fabricating chips,integrated circuits, monolithic devices, semiconductor devices, andmicroelectronic devices, such as display devices. For example, FIG. 4illustrates an embodiment of a display device such as an active-matrixliquid-crystal display (AMLCD) 480. In FIG. 4, the AMLCD 480 can includepixel devices (i.e., liquid crystal elements) 440 in a matrix of adisplay area 460. The pixel devices 440 in the matrix can be coupled tothin-film transistors 400 also located in the display area 460. Thethin-film transistor 400 can include embodiments of the thin-filmtransistors as disclosed herein. Additionally, the AMLCD 480 can includeorthogonal control lines 462 and 464 for supplying an addressable signalvoltage to the thin-film transistors 400 to influence the thin-filmtransistors to turn on and off and control the pixel devices 440, e.g.,to provide an image on the AMLCD 480.

Although specific exemplary embodiments have been illustrated anddescribed herein, those of ordinary skill in the art will appreciatethat an arrangement calculated to achieve the same techniques can besubstituted for the specific exemplary embodiments shown. Thisdisclosure is intended to cover adaptations or variations of theembodiments of the disclosure. It is to be understood that the abovedescription has been made in an illustrative fashion, and not arestrictive one.

Combination of the above exemplary embodiments, and other embodimentsnot specifically described herein will be apparent to those of skill inthe art upon reviewing the above description. The scope of the variousembodiments of the disclosure includes other applications in which theabove structures and methods are used. Therefore, the scope of variousembodiments of the disclosure should be determined with reference to theappended claims, along with the full range of equivalents to which suchclaims are entitled.

In the foregoing Detailed Description, various features are groupedtogether in a single exemplary embodiment for the purpose ofstreamlining the disclosure. This method of disclosure is not to beinterpreted as reflecting an intention that the embodiments of thedisclosure necessitate more features than are expressly recited in eachclaim. Rather, as the following claims reflect, inventive subject matterlies in less than all features of a single disclosed exemplaryembodiment. Thus, the following claims are hereby incorporated into theDetailed Description, with each claim standing on its own as a separateembodiment.

1. A semiconductor device, comprising: a drain electrode; a sourceelectrode; a channel contacting the drain electrode and the sourceelectrode, wherein the channel includes one or more metal oxides thatinclude zinc-gallium, cadmium-gallium, and cadmium-indium, and whereinat least one metal oxide of the channel is of an amorphous form; a gateelectrode; and a gate dielectric positioned between the gate electrodeand the channel.
 2. The semiconductor device of claim 1, wherein themetal oxide includes an atomic composition of metal (A)-to-metal (B)ratio (A:B), wherein A and B are each in a range of about 0.05 to about0.95.
 3. The semiconductor device of claim 1, wherein the metal oxidesinclude at least one of a single-phase crystalline form, and amixed-phase crystalline form.
 4. The semiconductor device of claim 1,wherein the metal oxide includes one or more of zinc-gallium oxide,cadmium-gallium oxide, cadmium-indium oxide.
 5. The semiconductor deviceof claim 4, where the metal oxide includes an atomic composition ofmetal(A)-to-metal(B) ratio (A:B), wherein A and B are each in a range ofabout 0.05 to about 0.95.
 6. The semiconductor device of claim 1,wherein the channel includes one or more compounds of the formulaA_(x)B_(x)C_(x)O_(x), wherein each A is selected from the group of Zn,Cd, each B is selected from the group of Ga, In, each C is selected fromthe group of Zn, Cd, Ga, In, each O is atomic oxygen, each x isindependently a non-zero integer, and wherein each of A, B, and C aredifferent.
 7. The semiconductor device of claim 6, wherein the one ormore compounds of the formula A_(x)B_(x)C_(x)O_(x) includes an atomiccomposition of ratio A:B:C, wherein A, B, and C are each in a range ofabout 0.025 to about 0.95.
 8. The semiconductor device of claim 1,wherein the metal oxide includes one or more of zinc-gallium-indiumoxide, cadmium-gallium-indium oxide, zinc-cadmium-gallium oxide,zinc-cadmium-indium oxide.
 9. The semiconductor device of claim 8,wherein the metal oxide includes an atomic composition of ration A:B:C,wherein A, B, and C are each in a range of about 0.025 to about 0.95.10. The semiconductor device of claim 6, wherein the one or morecompounds of formula A_(x)B_(x)C_(x)O_(x), includes D_(x), to form acompound of the formula A_(x)B_(x)C_(x)D_(x)O_(x), wherein D is selectedfrom the group of Zn, Cd, Ga, In, each O is atomic oxygen, each x isindependently a non-zero integer, and wherein each of A, B, C, and D aredifferent.
 11. The semiconductor device of claim 10, wherein the one ormore compounds of the formula A_(x)B_(x)C_(x)D_(x)O_(x) includes anatomic composition of ratio A:B:C:D, wherein A, B, C, and D are each ina range of about 0.017 to about 0.95.
 12. The semiconductor device ofclaim 1, wherein the metal oxide includes one or more of includingzinc-cadmium-gallium-indium oxide.
 13. The semiconductor device of claim12, wherein the metal oxide includes an atomic composition of ratioA:B:C:D, wherein A, B, C, and D are each in a range of about 0.017 toabout 0.95.
 14. A semiconductor device, comprising: a drain electrode; asource electrode; means for controlling current flow electricallycoupled to the drain electrode and the source electrode, wherein themeans for controlling current flow is comprised at least partially of achannel in amorphous form; a gate electrode separated from the channelby a gate dielectric; and wherein the channel includes one or morecompounds selected from the group of formulas including A_(X)B_(X)O_(X),A_(X)B_(X)C_(X)O_(X), and A_(X)B_(X)C_(X)D_(X)O_(X), and wherein each Ais selected from the group of Zn, Cd, each B is selected from the groupof Ga, In, each C and D is selected from the group of Zn, Cd, Ga, In,each 0 is atomic oxygen, each x is independently a non-zero integer, andwherein each of A, B, C, and D are different.
 15. The semiconductordevice of claim 14, wherein the means for controlling current flowincludes forming the channel using metal oxides at least one of anamorphous form, a single-phase crystalline form, and a mixed-phasecrystalline form.
 16. The semiconductor device of claim 14, wherein thesource, drain, and gate electrodes include a substantially transparentmaterial.
 17. A semiconductor device formed by steps, comprising:providing a drain electrode; providing a source electrode; providing aprecursor composition consisting of one or more precursor compoundsselected from the group consisting of: zinc oxide, cadmium oxide,gallium oxide, indium oxide, zinc-gallium oxide, cadmium-gallium oxide,and cadmium-indium oxide; depositing a channel including the precursorcomposition to form a multicomponent oxide from the precursorcomposition contacting the drain electrode and the source electrode,wherein the multicomponent oxide is of an amorphous form; providing agate electrode; and providing a gate dielectric positioned between thegate electrode and the channel.
 18. The semiconductor device of claim17, wherein the step for depositing a channel includes an ink-jetdeposition technique.
 19. The semiconductor device of claim 17, whereinthe precursor composition includes one or more precursor compounds thatinclude A_(x), one or more precursor compounds that include B_(x), oneor more precursor compounds that include C_(x), wherein each A isselected from the group of Zn, Cd, each B is selected from the group Ga,In, each C is selected from the group of Zn, Cd, Ga, In, each x isindependently a non-zero integer, and wherein each of A, B, and C aredifferent.
 20. The semiconductor device of claim 19, wherein the one ormore precursor compounds includes one or more precursor compounds thatinclude D_(x), wherein D is selected from the group of Zn, Cd, Ga, In,each x is independently a non-zero integer, and wherein each of A, B, C,and D are different.
 21. The semiconductor device of claim 20, whereindepositing the channel includes vaporizing the precursor composition toform a vaporized precursor composition, and depositing the vaporizedprecursor composition using a physical vapor deposition techniqueincluding one or more of dc reactive sputtering, rf sputtering,magnetron sputtering, ion beam sputtering.
 22. A method for operating asemiconductor device, comprising: providing a semiconductor device thatincludes a source electrode, a drain electrode, and a channel toelectrically couple the source electrode and the drain electrode, a gateelectrode separated from the channel by a gate dielectric, wherein thechannel includes a multicomponent oxide including at least one metalcation from group 12, and at least one metal cation from group 13,wherein group 12 cations includes Zn and Cd, and group 13 cationsincludes Ga and In, to form at least one of a three-component oxide, afour-component oxide, and a two-component oxide that includeszinc-gallium oxide, cadmium-gallium oxide, cadmium-indium oxide, whereinat least one of the two-, three-, and four-component oxides is formed ofan amorphous form; and applying a voltage to the gate electrode toeffect a flow of electrons through the channel.
 23. The method of claim22, wherein operating the semiconductor device includes using thesemiconductor device as a switch in a display device.
 24. The method ofclaim 22, wherein operating the semiconductor device includes conductingelectrons through the channel in a region of linear conductivity.
 25. Adisplay device, comprising: a plurality of pixel devices configured tooperate collectively to display images, where each of the pixel devicesincludes a semiconductor device configured to control light emitted bythe pixel device, the semiconductor device including: a drain electrode;a source electrode; a channel contacting the drain electrode and thesource electrode, wherein the channel includes one or more metal oxidesthat include zinc-gallium, cadmium-gallium, and cadmium-indium, andwherein at least one metal oxide of the channel is of an amorphous form;a gate electrode; and a gate dielectric positioned between the gateelectrode and the channel and configured to permit application of anelectric field to the channel.
 26. The display of claim 25, wherein thesource, the drain, and the gate electrodes include a substantiallytransparent material.
 27. The display of claim 25, wherein the metaloxide includes an atomic composition of metal(A)-to-metal(B) ratio(A:B), wherein A and B are each in a range of about 0.05 to about 0.95.28. The display of claim 25, wherein the channel includes one or morecompounds of the formula A_(X)B_(X)C_(X)O_(X), wherein each A isselected from the group of Zn, Cd, each B is selected from the group ofGa, In, each C is selected from the group of Zn, Cd, Ga, In, each O isatomic oxygen, each x is independently a non-zero integer, and whereineach of A, B, and C are different.
 29. The display of claim 28, whereinthe one or more compounds of the formula A_(X)B_(X)C_(X)O_(X) includes aratio of A:B:C, wherein A, B, and C, are each in a range of about 0.025to about 0.95.
 30. The display of claim 28, wherein the one or morecompounds of formula A_(X)B_(X)C_(X)O_(X), includes D_(X), to form acompound of the formula A_(X)B_(X)C_(X)D_(X)O_(X), wherein D is selectedfrom the group of Zn, Cd, Ga, In, each O is atomic oxygen, each x isindependently a non-zero integer, and wherein each of A, B, C, and D aredifferent.
 31. The display of claim 30, wherein the one or morecompounds of the formula A_(X)B_(X)C_(X)D_(X)O_(X) includes a ratio ofA:B:C:D, wherein A, B, C, and D, are each in a range of about 0.017 toabout 0.95.
 32. The display of claim 25, wherein the one or more metaloxides include at least one of a single-phase crystalline form, and amixed-phase crystalline form.